Recently, a universal serial bus (so-called USB) has widely been spread as an interface between a host computer (to be referred to as a host hereinafter) and a printing apparatus called a printer.
USB transfer modes include several types. Data transfer between a host and a printer generally utilizes a bulk transfer mode. In bulk transfer, the host transfers data for each packet having a specific number of bytes. The printer sends back a signal ACK if correctly receiving the transferred packet, or a signal NACK if failing to receive any packet due to some reason.
The host transmits the next data if receiving a signal ACK, or the same data to the printer again if receiving an NACK signal.
Independently of this operation, the host transmits to the printer a status response request which requests the printer to send the current printer status. Upon reception of this status response request, the printer sends back the current printer status such as a normal state or error occurrence. In general, the status request sequence is executed at a predetermined time interval.
The printer cannot receive data when the reception buffer in the printer becomes full. The reception buffer becomes full in, e.g., a case wherein long-time head cleaning is performed, a case wherein a cooling period is required due to excessive temperature rise of the printhead, a case wherein printing cannot be done in the absence of any sheet or ink in the printer, and a case wherein printing cannot be done due to a sheet jam in the printer.
Of these cases, two former cases are free from any error, and print processing can continue again after the end of processing. In two latter cases, however, an error occurs, and the user must do some processing.
A host which incorporates a recent Windows OS displays a time-out error dialog for a long NACK signal return period.
As described above, conditions for a long NACK signal return period include cleaning processing free from any error.
In the conventional control method, conditions for a long NACK signal return period include cleaning processing free from any error. Even in such a case, if the user recognizes the time-out error dialog on the host, he/she may cancel printing.
To avoid this, it must be prevented to generate the dialog by the host until the host grasps the state of a peripheral device, and to prolong the continuous NACK signal return period.
A serial interface such as an RS-232C interface other than a USB interface has a status signal for monitoring the operation status of a device by using a signal DTR, as disclosed in Japanese Patent Laid-Open No. 10-333856. The USB interface does not have such status signal.
Basic circuits for USB interface circuits have been developed by a plurality of vendors (inSilicon, NEC, and the like). Designers for printing apparatuses design the circuits of printing apparatuses by building in interface circuit macros. However, the USB interface circuit does not have a function of building in a macro a status signal like one prepared for the RS-232C interface. In addition, any change in USB interface circuit is forbidden.